The use of windmills and water wheels to drive a generator that, in turn, produces electrical power is well known in the art. The efficiency with which a windmill or water wheel converts fluid power into usable shaft power is primarily dependent upon the design of the vane and the mechanism used to support the vane.
Two basic windmill designs are presently in use: those having horizontal axis of rotation and those having vertical axis of rotation. The windmills with a vertical axis rotor have a major advantage over horizontal axis rotors in that they do not have to be turned into the wind as the direction of the wind changes. Thus, the design parameters for vertical axis windmills are less stringent because the forces that apply stress on the vanes or blades, bearings and other moving components are eliminated.
The efficiency of a vertical axis windmill is dependent upon the efficiency of its vanes. The net efficiency is the difference between the power extracted from the wind when the vane is moving with the wind, less the drag produced when the vane is moving against the wind. The prior art vertical drag windmills generally have relatively high starting torques. However, they also have relatively low power outputs per given rotor size and weight.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention however, the following U.S. patents were considered related:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 4,684,817 Goldwater 4 August 1987 4,545,729 Storm 8 October 1985 4,530,642 Yang 23 July 1985 4,457,669 Corry 3 July 1984 ______________________________________
The Goldwater patent discloses a windmill that rotates in a horizontal plane about a vertical axis. The design includes essentially radial vanes where each vane is effectively a one way valve respective to air flow and each enhances the beneficial actions of the others. The vanes in operation, effectively simulate a sailing vessel navigating a circular course in wind of constant direction. Each of the vanes includes a framework which supports a grid that, in turn, is the supporting means for a plurality of pivotally connected, vertically aligned and overlapping light weight flexible sails. The sails are automatically rotated about the pivotal connection by the force of the wind into positions promoting the revolution of the windmill.
The Storm patent discloses a vertical axis of rotation wind turbine that utilizes sail elements. The elements include flexible sails which may be furled and unfurled in response to the speed of the wind, and which utilize a weight system for varying the area of the sail elements exposed to the wind.
The Yang patent discloses an improved windmill mechanism for adjusting the position of a wind responsive assembly in relation to the wind. The mechanism consists of a fabric sail mounted on the end of an arm which extends from a power output shaft. A torque sensor is disposed on the arm to sense the torque contribution through the arm to the power output shaft in response to wind acting upon the fabric sail. The position of the fabric sail is adjusted on the arm by means of a control processor which controls a trim motor and a magnetic brake.
The Corry patent discloses a sail-type windmill that provides high torque without limitations to size. Three sails are mounted to a frame for rotation about an axis generally parallel to the planes of the sails. The sails are flexible and sheets are provided for mounting the sails. Roller reefing is provided for modifying the effective area each sail member presents to the wind, including a spring biased weight associated with each sail and a line extending from the weight for effecting take-up and let-out of the sail and the sheet in response to radial movement of the weight.